Sections of tubing between sources of fluids, typically gases under pressure and an appliance often have connections which are either joints or fittings.
A joint is a connection that is either threaded or welded and is most often used with rigid pipe. A fitting is most often found on tubing and forms the seal with compression or a flare. Fittings require at least one nut but more often contain two or more.
Leaks in fittings occur for a variety of reasons and often such leaks are difficult and expensive to locate and repair. As far as I am aware, there is no way prior to the present invention by which an established fitting, whether compression or a flared fitting, can be so locked as to ensure against leaking.